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Thread: A high gain CP OMNI finally! Parasitic Lindenblad

  1. #11
    Navigator Kondor-FPV's Avatar
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    Hello Hugo,
    yes, I could do that, you can analyze 5.8 also?
    That would be fantastic.

    I can make you one identical to this.
    www.fpvlr.com - Home of your favourite Custom FPV antennas.

  2. #12
    Navigator Kondor-FPV's Avatar
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    Quote Originally Posted by bgarber View Post
    Kondor, please forgive my "noob-ness" here but I have a question about the element distance. When you calculate 0.15 lambda to get 30.1 mm, are you using a velocity factor of 0.87?

    I saw an article about Parasitic Lindenblad antennas for 70cm in an AMSAT (Radio Amateur Satellite Corporation) publication... www.stalad.it/iz4bqv/antspec/2006ParaLindy.pdf

    Very interesting! When can we expect to see some production models for sale???
    The velocity factor depends on the material used for a standoff, I used that velocity factor on my 5.8 but I don't expect it to be correct for wood distancer or plastic distancer or pvc etc, which do affect a bit and cover up the dipole parasitic elements.
    Actually in free air it would be about 34 mm, but I expect Alex to have to move it to 31-32mm in his modeling.

    I would probably wait for Hugo to analyze the 5.8 antenna if he confirms he has the capability.
    I do not want to make the mistake of advertising false information. I liked the perfomance but I don't know how repeatable it is.
    I will send a couple to hugo to see if they can be reliably replicated.
    www.fpvlr.com - Home of your favourite Custom FPV antennas.

  3. #13
    Navigator Kondor-FPV's Avatar
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    Hello Hugo,
    in 2-3 hours I am going to test out the two antennas that I will send you.
    I made one with high angle of 55 , and I will make one with lower angle for the parasitic elements.

    This one resonates higher, incredible how bad the stock foxtec antennas are... they are tuned WAAAY high around 6+ ghz,
    After the circulator unit was put in place it came in with a decent swr at 5945... so I am going to fly it at that frequency.
    www.fpvlr.com - Home of your favourite Custom FPV antennas.

  4. #14
    Navigator Kondor-FPV's Avatar
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    the 5.8 circulator is really tiny, this is the 3rd version for a lower angle incline.
    You can see the tolerances... you have to have a good cnc machine for this or a laser cutter.
    www.fpvlr.com - Home of your favourite Custom FPV antennas.

  5. #15
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    Even if it is small..everything can be made in enough tries...So I hope you will be a nice bloke and scan the circulator, make a pdf and post it on fpvlab..Since I have access to a VNA I could make them and tune them myself..Hope you will be cooperative..Will you make a tutorial? Is this both a rx and tx antenna?

  6. #16
    Engineer for Jesus Christ IBCrazy's Avatar
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    Now I see how it works! It's like a yagi. Dipole in the middle with parasitic elements to direct the signal. I didn't realize that it could actually rotate it. You learn something new every day.

    One thing that might cause an issue is the dielectric right in the middle of the radiation pattern. If you can move the support up or down, it might help. Or here's another suggestion: Use two supports with the elements in between them. This will give it more support and help clear the center of the radiation pattern where reactivity is critical. If you play your cards right, you can make this a commercial product... and I'll be your first customer

    Here's and idea for you: Make a cap for the cheap dipoles that come with most systems that all you need to do is insert the elements.

    Needless to say I am very excited for you, Kondor. Very excited!

    -Alex
    If it is broken, fix it. if it isn't broken, I'll soon fix that.

    videoaerialsystems.com - Performance video piloting

  7. #17
    Engineer for Jesus Christ IBCrazy's Avatar
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    I am getting empirical numbers for a 55 degree tilt from vertical for best axial ratio. However, the distance changes with the location and type of dielectric. Tilt stays the same. What material are you using? FR4?

    -Alex
    If it is broken, fix it. if it isn't broken, I'll soon fix that.

    videoaerialsystems.com - Performance video piloting

  8. #18
    Just dog tired. Wearyman's Avatar
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    I have to say that although I don't understand 90% of what you guys are saying, I'm still really excited about the potential for an awesome new antenna product, particularly one that promises to turn crappy cheap rubber duck antennas into awesome and powerful CP antennas!

    I wonder how having some kind of plastic cover over the antenna elements (to protect against damage) would affect the signal and geometry of this thing?

  9. #19
    I Like Waffles... SENTRY's Avatar
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    Good to see you antenna gurus geek out - I love it. I'm just a pilot - but you guys geeking out makes my life easier and brings my planes home from some of the toughest places I put them. Good job!
    "I Like Waffles" : FPVLab on Facebook and FPVLab on Twitter

  10. #20
    Navigator Kondor-FPV's Avatar
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    Yes Alex,
    I am using Fr4, it's 1.5mm thick and I made the arms 2mm wide... that's for 5.8 of course, you are working on 1.3
    This is what my last antenna looks like, with 32 angle so not far from the original paper...
    I want to fly right now, plane is ready and charged but there are 40mph wind gusts out there, I hate it when it does that right at the moment I decide I want to fly.

    P.S -you can try with a 4.4 dielectric coefficient for the fr4
    www.fpvlr.com - Home of your favourite Custom FPV antennas.

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